1. Field of the Invention
The present invention relates generally to agricultural planters having sensors for counting seeds as the seeds are dropped from a seed metering mechanism. In particular, the present invention relates to improvements in seed tubes and sensor arrangements for use with such agricultural planters.
2. Description of the Related Art
There are several styles of seed meters used on agriculture equipment manufactured today. A lot of time and expense are spent on getting perfect seed spacing out of the meter, which is intended to give perfect plant-to-plant spacing in the field in order to maximize yields. To get perfect plant spacing, each seed has to be singulated and then released from the meter at a precise, repeatable time. A seed tube is used on these planters to guide and protect the seed on it's journey from the seed meter to the open furrow in the ground.
The seed dropping out of the seed meters is typically monitored by a seed sensor, usually an electric eye that can detect a seed as it passes by. Some of the early sensors were used to detect blockage or to detect the absence of seed. As improvements were made, the sensors were able to count individual seeds and give a farmer planting population feedback.
In the past few years, some sensors and the supporting software have the ability to do live statistical analysis on the seed, giving the operator a very accurate look into the quality of the seed spacing.
The seed sensor is typically mounted on the seed tube about half way between the seed entrance end (seed meter) and the exit end (ground). The basic seed tube sensor has two components, a transmitter and a receiver. Light is typically transmitted through a hole in the back of the seed tube and is detected through a hole in the front of the seed tube.
One of the challenges in implementing this type of sensor is to make sure the sensor itself does not hit the seed and cause disruptions to the seed spacing. The Applicants have discovered that conventional seed sensors often have slight imperfections that affect the seed trajectory as the seed travels through the seed tube, and thus have an effect on seed spacing out the bottom of the seed tube.
With the aid of the latest sensor equipment, the Applicants have monitored and developed statistics on the seed spacing coming out of the meter, and again at the bottom of the seed tube (ground). The Applicants found that the sensors used in conventional planter seed tubes were causing seed spacing problems at the exit end of the seed tube.
Sensors on the seed tubes can cause spacing problems for the following reasons. A “perfect” seed meter introduces seeds into the top of the seed tube that are perfectly spaced. The seeds fall to the ground at the same speed and have the same trajectory inside the seed tube. The distance between the seeds must be maintained inside the seed tube so that the seeds exit the seed tube with this same perfect spacing. If a seed hits or glances off even the slightest obstruction, the trajectory of the seed is altered and the seed takes longer to reach the bottom exit of the tube. Any seed that deviates from the path of the majority of the seeds is delayed and can be detected with modern sensor equipment. These small delays also cause irregular plant spacing in the field, which has been shown to cause yield loss. If this delay is great enough, the seed will lag and arrive at the exit at the same time as the next seed resulting in a “double” and leaving the seed's intended place in the field empty.
There have been attempts over the years to solve this problem, including the following:
1. Ramp. A ramp system for a seed tube is described in U.S. Pat. No. 5,533,458 issued to Bergland et al., which causes the seed to jump over and never make contact with the imperfections on the sensor face.
2. Setback. A setback arrangement for a seed tube is described in U.S. Pat. No. 6,332,413 issued to Stufflebeanm et al., in which the sensor and the entire lower portion of the seed tube are shifted so the seed becomes airborne for a brief time and never makes contact with the seed sensor face.
3. Smooth face. The sensor is manufactured with a smooth face and inserted in a hole in the seed tube. By controlling the wall thickness of the seed tube and the height of the sensor's face, the face ends up flush with the inside surface of the seed tube.
4. Transparent seed tube. A transparent seed tube is described in U.S. Patent Publication No. 2007/0084387 of Mariman et al. A transmitter of the sensor is positioned outside of the transparent side wall and operates through the transparent material.
The first and second attempted solutions described above tend to degrade the spacing due to an introduction of an extra bounce to get the seed over the sensor.
The third and fourth attempted solutions described above are attempts to provide a smoother inside surface of the seed tube. However, with respect to the third attempted solution, it is difficult to manufacture a smooth sensor face, and difficult to insert the sensor so it ends up exactly flush with the inside wall of the seed tube. All dimensions involved have to be held in very close tolerance to make this system work. Gaps, steps, and ledges, no matter how small, can cause spacing problems. As an example, a piece of transparent tape on the inside of the seed tube is enough of a bump to cause problems.
The transparent seed tube described in Mariman et al.'s '387 publication offers a partial solution to the problems described above. However, Mariman et al.'s seed tube includes a conventional lower locator hook molded into the front wall of the seed tube body. The conventional hook tends to create a sink and warp the interior surface of the front wall of the seed tube during manufacture. As a result, the interior surface of the front wall of Mariman et al.'s seed tube is not smooth and uninterrupted. Mariman et al.'s seed tube also has a substantial sensor pocket and mounting structure molded into the front wall for positioning the sensor, which may cause additional sinking and warping on the interior surface during the molding process.
Thus, there is a need in the industry for an improved seed tube and sensor assembly to improve seed spacing in an agricultural planter.